Friday, June 27, 2014

Humans have a well-documented tendency to see winning and losing streaks in situations that, in fact, are random. But scientists disagree about whether the "hot-hand bias" is a cultural artifact picked up in childhood or a predisposition deeply ingrained in the structure of our cognitive architecture.

Now in the first study in non-human primates of this systematic error in decision making, researchers find that monkeys also share our unfounded belief in winning and losing streaks. The results suggests that the penchant to see patterns that actually don't exist may be inherited—an evolutionary adaptation that may have provided our ancestors a selective advantage when foraging for food in the wild, according to lead author Tommy Blanchard, a doctoral candidate in brain and cognitive sciences at the University of Rochester.

The cognitive bias may be difficult to override even in situations that are truly random. This inborn tendency to feel that we are on a roll or in a slump may help explain why gambling can be so alluring and why the stock market is so prone to wild swings, said coauthor Benjamin Hayden, assistant professor brain and cognitive sciences at the University of Rochester.

While preferring silence to music from the West, chimpanzees apparently like to listen to the different rhythms of music from Africa and India, according to new research published by the American Psychological Association.

"Our objective was not to find a preference for different cultures' music. We used cultural music from Africa, India and Japan to pinpoint specific acoustic properties," said study coauthor Frans de Waal, PhD, of Emory University. "Past research has focused only on Western music and has not addressed the very different acoustic features of non-Western music. While nonhuman primates have previously indicated a preference among music choices, they have consistently chosen silence over the types of music previously tested."

Previous research has found that some nonhuman primates prefer slower tempos, but the current findings may be the first to show that they display a preference for particular rhythmic patterns, according to the study. "Although Western music, such as pop, blues and classical, sound different to the casual listener, they all follow the same musical and acoustic patterns. Therefore, by testing only different Western music, previous research has essentially replicated itself," the authors wrote. The study was published in APA's Journal of Experimental Psychology: Animal Learning and Cognition.

When African and Indian music was played near their large outdoor enclosures, the chimps spent significantly more time in areas where they could best hear the music. When Japanese music was played, they were more likely to be found in spots where it was more difficult or impossible to hear the music. The African and Indian music in the experiment had extreme ratios of strong to weak beats, whereas the Japanese music had regular strong beats, which is also typical of Western music.

"Chimpanzees may perceive the strong, predictable rhythmic patterns as threatening, as chimpanzee dominance displays commonly incorporate repeated rhythmic sounds such as stomping, clapping and banging objects," said de Waal.

Old World monkeys have undergone a remarkable evolution in facial appearance as a way of avoiding interbreeding with closely related and geographically proximate species, researchers from New York University and the University of Exeter have found. Their research provides the best evidence to date for the role of visual cues as a barrier to breeding across species.

“Evolution produces adaptations that help animals thrive in a particular environment, and over time these adaptations lead to the evolution of new species,” explains James Higham, an assistant professor in NYU’s Department of Anthropology and the senior author of the study, which appears in the journal Nature Communications. “A key question is what mechanisms keep closely related species that overlap geographically from inter-breeding, so that they are maintained as separate species.

“Our findings offer evidence for the use of visual signals to help ensure species recognition: species may evolve to look distinct specifically from the other species they are at risk of inter-breeding with. In other words, how you end up looking is a function of how those around you look. With the primates we studied, this has a purpose: to strengthen reproductive isolation between populations.”

“Our observation is quite unique in the sense that nothing seems to be communicated by it,” says study author Edwin van Leeuwen, a primate expert at the Max Planck Institute in The Netherlands.

To figure out if this was really a tradition, and not just chimpanzees sticking grass in their ears at random, van Leeuwen and his colleagues spent a year observing four chimp groups in Chimfunshi Wildlife Orphanage Trust, a sanctuary in Zambia. Only one troop performed the grass-in-ear behavior, although all of the chimps lived in the same grassy territory. There’s no genetic or ecological factors, the scientists believe, that would account for this behavior -- only culture.

Lydia Luncz, a primatologist at the Max Planck Institute in Leipzig, Germany, who was not involved with the research, agrees. This study shows how the chimpanzees who learned to put grass in their ears did so through the “natural transmission” of new behavior, she says.

The cultural quirk first popped up in 2010 when a chimpanzee, named Julie, was spotted sporting a long-stemmed piece of grass.

Tuesday, June 17, 2014

Adults today are more likely to have herpes — oral or genital — than not. But where did this widespread disease come from?

To answer that question, you’ll have to go back millions of years, to a time before we were human.

New genomic analysis has found that oral herpes may have been around since before our split with chimpanzees happened about 6 million years ago. The virus then branched out and followed the evolution of hominids to become oral herpes, or herpes simplex virus 1 (HSV-1).

“The ancestor of all monkeys and apes had the herpes virus,” said study author and virologist Joel Wertheim of the University of California at San Diego. “When the host species lineage started to split, the viruses also formed new lineages.”

The virus responsible for genital herpes hit our ancestors later, likely jumping from proto-chimps to a now-extinct hominid — either Homo habilis or Homo erectus — about 1.6 million years ago. The ancient virus eventually gave rise to what is now known as herpes simplex virus 2 (HSV-2) in humans, commonly spread through sexual contact.

Because the chimpanzee herpes simplex virus found its way back into our lineage, we are the only primate species known to be infected with two distinct herpes simplex viruses. But how the transmission occurred from primate-to-hominid all those years ago remains a mystery.

“We can’t say whether the interaction that led to cross-transmission was physical aggression or sexual contact,” Wertheim said. “We just don’t know, but both are possible.”

Alternate means could have been through hominids hunting and eating the meat of proto-chimps or living with them in close quarters, said virologist Alberto Severini of the University of Manitoba, who was not involved in the research.

Wednesday, June 11, 2014

Researchers at the California Institute of Technology have found that chimpanzees at the Kyoto University Primate Research Institute are consistently better at humans when playing simple competitive games.

In one game, called the Inspection Game, chimps and humans played a variation on hide-and-seek. In pairs of their own species (humans and chimps did not directly compete with each other for the study), the players sit back-to-back, each with a computer screen in front of them. After pushing a circle on the screen, they have to choose one of two boxes, right or left. They are then shown their opponent's selection.

Each player has a different role. The "mismatchers" have to choose the opposite of their opponent's selection, while the "matchers" have to choose the same as their opponent's selection. Each game lasted 200 rounds, and players that "won" a round were given a reward. In order to consistently win, players had to be able to anticipate their opponent's choices.

In game theory, there is a concept known as the Nash equilibrium. This means the balance that can be achieved when each player knows their opponent's strategies, but has nothing to gain by changing their own strategy. The 16 Japanese students participating in the study performed as expected: slow to learn their opponents' strategies, and not reaching the Nash equilibrium.

The six chimpanzees, however, learned the game and their opponents' moves rapidly, very nearly reaching the Nash equilibrium, even when the researchers swapped the chimps' roles and introduced higher rewards for specific choices. As the game changed, the chimps changed their strategies accordingly.